Referring to FIG. 2, an outline of a submerged type of a wire electrical discharge machine, as an example of an electrical discharge machine, will be described.
In the wire electrical discharge machine 100, a column 30 is set up on a base 20, and its upper part projects horizontally to form a horizontal portion 40. An upper nozzle 25 is located under the distal end of the horizontal portion 40. A lower arm 60 is fixed horizontally to the lower part of the column 30, and a lower nozzle 70 is provided on its distal end, facing the upper nozzle 25. The base 20 is further provided with an XY-table 80, which carries a submerged tank 90 thereon. Thus, the submerged tank 90 is moved in the X- and Y-directions with respect to the base 20.
One side wall of the submerged tank 90 is formed with. a window hole 120, which has a size large enough to allow the passage of the lower arm 60 and a Y-direction movement of the submerged tank 90 relative to the lower arm 60. A sealing plate 110, which is penetrated by the lower arm 60, can always close the window hole 120 while the submerged tank 90 moves in the Y-direction with respect to the lower arm 60. Also, the lower arm 60 can advance and retreat in its longitudinal direction with respect to the sealing plate 110. Therefore, even though the submerged tank 90 moves in the X- and Y-directions with respect to the lower arm 60, a sealed state between the submerged tank 90 and the lower arm 60 can be maintained at all times.
A supply reel 140, a braking roller 150, and a feed roller D are pivotally mounted on the front surface of the column 30. Further, guide rollers A, B and C are pivotally mounted on the distal end side of the lower arm 60, the inner surface of the sealing plate 110, and the upper end of a stay 130, that is fixed to the sealing plate 110, respectively. A wire electrode (hereinafter referred to simply as wire) 160 drawn out from the supply reel 140 reaches the lower arm 60 by way of the braking roller 150, upper nozzle 25, and lower nozzle 70, passes through the one side wall of the submerged tank 90, and reaches the feed roller D.
A workpiece (not shown) is placed between the upper nozzle 25 and the lower nozzle 70 in the submerged tank 90, and is moved integrally with the submerged tank 90. Thus, the workpiece moves in the X- and Y-directions with respect to the wire 160, and is cut out to a desired shape.
A handling robot is used to take out a cutout of the workpiece from the submerged tank after electrical discharge machining operation is finished. However, the handling robot must be given instructions for complex operation such as holding securely and taking out the workpiece machined to a unique shape, so that an operator is apt to be bound to carry out difficult operations.
As for the techniques for solving this problem and lightening the operator's burden, there are those disclosed in Japanese Patent Application KOKAI Nos. 60-201822 and 60-180726. According to these techniques, a workpiece handling robot equipped with an electromagnet, magnetic chuck, or suction cup is used to take out the workpiece or hold the cutout of the workpiece during the electrical discharge machining operation.
However, in the case of an electrical discharge machine disclosed in the above KOKAI No. 60-201822, a handling robot for removing a cutout of a workpiece is mounted on a workpiece carrying table. In such a case where a submerged tank is filled with water or oil for dipping, there is a problem such that the workpiece handling robot may be affected by moisture from the water, oil, etc.
On the other hand, in an electrical discharge machine disclosed in the above KOKAI No. 60-180726, a handling robot for removing a cutout of a workpiece is mounted integrally with a column of the electrical discharge machine. Thus, the position of the handling robot cannot be made to follow the movement of the workpiece carrying table that accompanies feed for machining. Therefore, during the electrical discharge machining operation, the handling robot cannot be made to perform the operation for holding the cutout of the workpiece and the like.
Moreover, in both of the electrical discharge machines disclosed in the aforesaid two publications, the handling robot for removing the cutout of the workpiece is mounted directly on or in close vicinity to the workpiece carrying table. In some cases, therefore, the existence of the handling robot become hindrance to operator's performance, especially when loading or unloading the workpiece or when preparing for machining operation.
Thus, it is conceivable to separate the handling robot from the body of the electrical discharge machine and place it on the floor on which the electrical discharge machine body is installed lest it should become a hindrance to the operation for attachment or detachment of workpiece. If this is done, however, the position of the handling robot cannot be made to follow the movement of the workpiece carrying table that accompanies the feed for machining. It is difficult, therefore, to enable the handling robot to hold the cutout of the workpiece during the electrical discharge machining operation.